Method and apparatus for controlling mercury arc rectifiers



Nov. 13, 1934. E. L. WHITE Filed Feb. 19. 1932 SUP/ 4 Y 2 3 a/a .9 f :1o r .w 36

0} Q6 1 -E v 3 [i 15 wnuuuu L 33 A-CYSJQ/Q/ 129. INVENTOR. Gd/WNW 9.Q0612 69 BY (9 I v ATTORNEY Patented Nov. 13, 1934 UNITED STATES PATENTOFFICE LING MERCURY Edwin L. White,

ARC RECTIFIERS Chevy Chase, Md.

Application February 19, 1932, Serial No. 594,139

11 Claims.

My invention relates broadly to mercury arc rectifiers and moreparticularly to means for controlling the operation of mercury arcrectifiers.

One of the objects of my invention is to provide a construction andarrangement of control means for a mercury arc rectifier by which a highpower rectifier maybe controlled from a remote positicn withoutmechanical movement of the rectifier.

1 Another object of my invention is to provide a construction of mercuryarc rectifier associated with a grid glow tube so arranged with respectto the electrodes of the mercury arc rectifier that ionization may beestablished within the mercury arc rectifier for initiating theoperation of the rectifier.

Still another object of my invention is to provide a construction ofgrid glow tube device associated with a mercury arc rectifier and havingcontrol circuits connected therewith for controlling the operation ofthe rectifier from a remote position.

Other and further objects of my invention reside in the construction ofmercury arc rectifier and grid glow tube associated therewith as setforth more fully in the specification hereinafter following by referenceto the accompanying drawing, in which:

Figure 1 schematically shows a mercury are 39 rectifier and associatedgrid glow tube constructed and arranged in accordance with my inventionand illustrating the circuits associated with the mercury arc rectifier;and Fig. 2 illustrates a modified circuit arrangement for the grid glowtube employed in the system of my invention.

My invention employs a grid glow tube in association with a mercury arcrectifier with control circuits extending from a remote position to thegrid glow tube for controlling the operation of 49 the grid glow tubeand correspondingly controlling the ionization within the mercury arcrectifier. The grid glow tube is arranged in such position with respectto the mercury arc rectifier that the grid glow tube may be operated toionize the gap between the electrodes of the mercury arc rectifier forestablishing a discharge path through the rectifier and starting andmaintaining operation of the arc without mechanical movement of therectifier. The grid glow tube is associated with the mercury arcrectifier in such manner that the electrodes of the grid glow tube areadjacent the discharge path of the mercury arc rectifier. Normally, alarge blocking or bias potential is applied to the grid electrode of thegrid glow tube, as a result of which no mercury ions will be formed ineither the grid glow tube or the mercury arc rectifier tube. If the gridbias is lowered, the gas between the cathode and anode of the grid glowtube is broken down and a current flows through the cathode and anodecircuit. The ions so produced are projected into the mercury arcrectifier tube through an opening in the anode. A conductive dischargepath is thereby established between the mercury pool electrode and theother electrodes within the mercury arc rectifier tube therebyestablishing the discharge path between the electrodes within themercury arc'rectifier tube. The mercury arc rectifier is then maintainedin operation p by the continued supply of energy thereto. In large sizemercury arc rectifier tubes employing a single pole rectifier instead ofa multiple pole rectifier, the arc is self extinguishing and in order tomaintain the are, I so arrange the circuit that the grid glow tubeoperates each semi-cycle Z to maintain the arc discharge. In this case,the mercury arc rectifier tube is operated only as long as the bias isoff the grid of the grid glow tube. A very small current is required forcontrolling the grid glow tube while permitting the control of largecurrents through the mercury arc rectifier without mechanical movement.The small current which is required to operate the grid glow tube may,therefore, be obtained through the operation of a thermostat or a smallswitch device.

Referring to the drawing in more detail, reference character 1designates the mercury arc rectifier tube having extensions 2 and 3thereon and including a central portion 4 which encloses the mercurypool 8 and to which electrical connection is made through electrode 7.Electrodes 5 and 6 are arranged in the extensions 2 and 3 of the mercuryarc rectifier tube. Power is supplied to the mercury arc rectifier tubethrough transformer 10 comprising primary winding 11 and secondarywinding 12. The opposite ends of secondary winding 12 are connectedthrough leads l4 and 15 with electrodes 5 and 6 respectively. The centerpoint of sec- 101} ondary winding 12 is connected through lead 16 withthe output of the mercury arc rectifier. The electrode 7 connectsthrough lead 17 to the output of the mercury arc rectifier.

The grid glow tube is represented at 20 formed in an extension on oneside of the mercury arc rectifier tube and connected through tubularportion 21 with the mercury arc rectifier tube 1.

An insulated terminal block 22 is provided on the envelope of the gridglow tube 20 and provides for the passage of conductors to the oathode23 inside the tube. Grid electrode 24 is mounted inside the envelope 20and is connected to the external control circuit as shown. The anode 25is arranged within the grid glow tube and is connected with the externalcircuit as shown. It will be observed that the anode 25 has a centralaperture 2511 which is aligned with the tubular portion 21, thuspermitting the projection of electrons into the discharge paths withinthe mercury arc rectifier tube 1. The cathode 23 is heated from currentsupplied from source of potential 26. The anode 25 is given an initialpositive potential from battery 27 connected in series between thecathode 23 and anode 25 as shown. The grid 24 is normally biased fromsource of potential 28 by connection to a point of negative potential onthe potentiometer 29, the potentiometer shunting the potential source28. A tap 30 is provided on potentiometer 29 and connected with thecontrol circuit 31 which may lead to a remote point and be controlled byswitch 31a located at the remote point. Closing of switchBla decreasesthe bias potential on grid 24 thus controlling the discharge ofelectrons from cathode 23 to anode 25 and the projection of suchelectrons through the aperture 25a in the anode 25 and into thedischarge path within the mercury arc rectifier tube 1. Upon openingswitch 31a, the blocking potential is again restored to the gridelectrode 24 thus preventing the further propagation of electrons intothe discharge path within the mercury arc rectifier tube.

I may employ alternating current in lieu of the direct current sourcesillustrated in Fig. 1. Fig. 2 illustrates the manner of employingalternating current for the control of the grid glow tube.

A power transformer 32 having primary winding 33, connected with thealternating current source, is provided with secondary windings 34 andv35. Secondary winding 34 provides heating potential for cathode 23.Secondary winding 35 provides a source of potential for charging theanode 25 and biasing the grid electrode 24. A tap 40 in secondarywinding 35 connects with tap 39 in secondary winding 34 thus completingthe external circuit connection from anode 25 to cathode 23.Potentiometer 36 is connected in shunt with the portion of secondarywinding 35 between tap 40 and the end of the secondary winding. Taps 37on the potentiometer 36 lead to the remote control circuit 31 whichincludes the control switch 31a at the control position. The controlcircuit'connects to grid 24 and when closed, operates to reduce the biaspotential and allow the projection of electrons through the aperture250. in anode 25 for ionizing the discharge paths within the mercury arcrectifier tube 1.

As heretofore noted, a single pole type of rectifierwhich will benormally self-extinguishing may be maintained in operation by the cyclicoperation of the grid glow tube so long as the bias potential on thegrid is of reduced value.

While I have described the control system in certain preferredembodiments, I desire that it be understood that modifications may bemade and that no limitations upon my invention are intended other thanare imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. A mercury arc rectifier including a tube enclosing a plurality ofdischarge paths, an extension on said tube, a grid glow tube connectedwith said extension with the axis of said grid glow tube aligned with atleast a portion of one of said discharge paths, a plurality ofelectrodes within said grid glow tube including a cathode, a controlgrid and an anode, and means'for projecting electrons from said gridglow tube through said anode into the discharge paths in said mercuryarc rectifier for ionizing the paths in said mercury arc rectifier tube.

2. A mercury arc rectifier comprising an enclosing vessel, a pluralityofelectrodes disposed within said vessel and arranged in gaseousdischarge paths, an extension at one side of said vessel in alignmentwith at least a portion of one of said discharge paths, a tube connectedwith said extension, a cathode in the remote and of said tube, a centrolgrid adjacent said cathode, and an anode adjacent said control grid andimmediately adjacent the gaseous discharge paths in said vessel andcircuits electrically connected with said cathode, control grid andanode for projecting electrons through said anode into said mercuryarcrectifier tube and ionizing the discharge paths therein. v

3. A mercury arc rectifier comprising a vessel enclosing a plurality ofdischargepaths, an extension at one side of said vessel co-linear withat least a portion of at least one of the discharge paths in saidvessel, a tube connected with said extension, a cathode disposed in oneend of said tube, a control grid mounted adjacent said cathode, an anodedisposed adjacent said control grid 4. A mercury arc rectifiercomprising a vessel enclosing a plurality of discharge paths, anextension at one side of said vessel co-linear with at least a portionof at least one of the discharge paths in said vessel, a tube connectedwithsaid extension, a cathode disposed in one end of said tube, acontrol grid mounted adjacent said cathode, an anode disposed-adjacentsaid control grid and constituting a target for bombardment by electronsemitted by said cathode and arranged immediately adjacent the connectionof said tube with said vessel, and direct current means for excitingsaid electrodes for projecting electrons into said vessel through saidanode and ionizing the discharge paths therein.

5. A mercury arc rectifier comprising a vessel enclosing a plurality ofdischarge. paths; an extension at one side of said-vessel co-linear withat least a portion of at least one of the discharge paths in saidvessel, a tube connected with said extension, a cathode disposed in oneend of said tube, a'control grid mounted adjacent said cathode, an anodedisposed adjacent said control grid and arranged immediately adjacentthe connection of said tube with said vessel, said anode hav--. ing a.central aperture therein, and alternatin current means for excitingsaid electrodes for projecting electrons into said vessel through saidanode and ionizing the discharge paths therein.

6. A mercury arc rectifier comprising a vessel enclosing a plurality ofdischarge paths, an extension at one side of said vessel co-linear withat least a portion of at. least one of the discharge paths in saidvessel, a tube connected with said extension, a cathode disposed in oneend of said tube, a control grid mounted. adjacent said cathode, saidanode comprising a plate apertured at its center and extending in aplane normal to the axis of the connection of'said tube with saidvessel, and means connected with said electrodes whereby said electrodesoperate to project electrons into said vessel through the apertured anode for ionizing said discharge paths.

7. A mercury arc rectifier comprising an enclosing vessel, a pluralityof discharge paths within said vessel, a tube connected with one side ofsaid vessel co-linear with at least a portion of at least one of thedischarge paths in said vessel, a cathode in one end of said tube, acontrol grid electrode in said tube adjacent said cathode, an anode insaid tube adjacent said control grid electrode, external circuits forenergizing said cathode and establishing a predetermined potentialbetween said cathode and said anode, means for establishing apredetermined negative potential upon said control grid electrode fornormally blocking the discharge of electrons from said tube into saidvessel, and means for reducing the negative potential on said controlgrid electrode for projecting electrons into the discharge paths withinsaid vessel through said anode for ionizing said paths.

8'. A mercury arc rectifier comprising an enclosing vessel, a pluralityof discharge paths within said vessel, a tube connected with one side ofsaid vessel co-linear with at least a portion of at least one of thedischarge paths in said vessel, a cathode in one end of said tube, acontrol grid electrode in said tube adjacent said cathode, an anode insaid tube adjacent said control grid electrode, external circuits forenergizing said cathode and establishing a predetermined potentialbetween said cathode and said anode, means for establishing apredetermined negative potential upon said control grid electrode fornormally blocking the discharge of electrons from said tube into saidvessel, a remote control circuit, a switch located at a remote point andconnected with said remote control circuit and connections between saidremote control circuit and said last mentioned means whereby thepotential on said control grid may be reduced and the electron dischargeinto said vessel may be reduced for effecting the projection ofelectrons into said vessel and ionizing said discharge paths.

9. A mercury arc rectifier comprising an enclosing vessel, a pluralityof discharge paths with in said vessel, a tube connected with one sideof said vessel co-linear with at least a portion of at least one of thedischarge paths in said vessel, a cathode in one end of said tube, acontrol grid electrode in said tube adjacent said cathode, an anode insaid tube adjacent said control grid electrode, external circuits forenergizing said cathode and establishing a predetermined potentialbetween said cathode and said anode, a source of potential, apotentiometer connected with said source of potential, connectionsbetween points of widely difierent potential on said potentiometer withsaid cathode and control grid electrode, a remote control circuit, aswitch in said remote control circuit in a remote control position, andconnections between said remote control circuit and points on saidpotentiometer for effectively reducing the potential on said controlgrid electrode when said switch is closed and effecting the discharge ofelectrons into said vessel for ionizing the discharge paths therein.

10. A mercury arc rectifier comprising a vessel enclosing a plurality ofdischarge paths, a tube connected with one side of said vessel co-linearwith at least a portion of at least one of the discharge paths in saidvessel, said tube enclosing a cathode, a control grid and an anode, asource of alternating current, a power transformer having a primarywinding connected with said source of alternating current, a pair ofsecondary windings, connections between said cathode and one of saidsecondary windings, a potentiometer connected between one end of saidsecond mentioned secondary winding and a tap in said second mentionedsecondary winding, taps on said potentiometer, a connection between oneof said taps and 1 0 said control grid, a connection between the anodeand the other end of said secondary winding, a remote control circuit, aswitch at a remote point in said remote control circuit, connectionsbetween said remote control circuit and the aforesaid tap on saidpotentiometer and to a second tap at an intermediate point on saidpotentiometer, whereby closing of said switch operates to reduce theefiective potential on said control grid for eiiccting the propagationof electrons into said vessel and ionizing the discharge paths therein.

11. A mercury arc rectifier comprising a vessel enclosing a plurality ofdischarge paths, a tube connected with one side of said vessel co-linearwith at least a portion of at least one of the discharge paths in saidvessel, a cathode in one end of said tube, a control grid electrodeadjacent said cathode, an anode adjacent said control grid electrode,said anode being apertured for the projection of electrons into thedischarge paths in said vessel, a source of alternating current, a powertransformer having its primary winding connected with said source, apair of secondary windings, one of said secondary windings connectedwith said cathode and the other of said secondary windings connectedwith said control grid and said anode for normally charging saidelectrodes and biasing said control grid for blocking the projection ofelectrons into said vessel, and means connected with said last mentionedsecondary 3 winding for reducing the biasing potential upon said controlgrid for effectively propagating electrons into said vessel for ionizingthe discharge paths therein.

